Do you have another FS?
Have you tried retouched the solder points on the sockets that hold the flip flops?
make sure the chips don't have bent or corroded pins?
It looks like the channel information goes from the PIC directly to the flip flops, and then to the sockets. with no other parts in between.
check over your rj45 jacks to make sure nothing shorted, or burnt, or corroded. check their solder joints.
If it's happening to particular channels, are they bunched together? (check more towards flip flops), or all across the board (rj45 connectors)